We used time‐lapse imagery, seismic and audio recordings, iceberg and glacier velocities, ocean wave measurements, and simple theoretical considerations to investigate the interactions between ...Jakobshavn Isbræ and its proglacial ice mélange. The mélange behaves as a weak, granular ice shelf whose rheology varies seasonally. Sea ice growth in winter stiffens the mélange matrix by binding iceberg clasts together, ultimately preventing the calving of full‐glacier‐thickness icebergs (the dominant style of calving) and enabling a several kilometer terminus advance. Each summer the mélange weakens and the terminus retreats. The mélange remains strong enough, however, to be largely unaffected by ocean currents (except during calving events) and to influence the timing and sequence of calving events. Furthermore, motion of the mélange is highly episodic: between calving events, including the entire winter, it is pushed down fjord by the advancing terminus (at ∼40 m d−1), whereas during calving events it can move in excess of 50 × 103 m d−1 for more than 10 min. By influencing the timing of calving events, the mélange contributes to the glacier's several kilometer seasonal advance and retreat; the associated geometric changes of the terminus area affect glacier flow. Furthermore, a force balance analysis shows that large‐scale calving is only possible from a terminus that is near floatation, especially in the presence of a resistive ice mélange. The net annual retreat of the glacier is therefore limited by its proximity to floatation, potentially providing a physical mechanism for a previously described near‐floatation criterion for calving.
Non-invasive brain stimulation (NIBS) probing the dorsolateral prefrontal cortex (DLPFC) has been shown to have little effect on working memory. The variability of NIBS responses might be explained ...by inter-subject brain anatomical variability. We investigated whether baseline cortical brain thickness of regions of interest was associated with working memory performance after NIBS by performing a secondary analysis of previously published research. Structural magnetic resonance imaging data were analyzed from healthy subjects who received transcranial direct current stimulation (tDCS), intermittent theta- burst stimulation (iTBS), and placebo. Twenty-two participants were randomly assigned to receive all the interventions in a random order. The working memory task was conducted after the end of each NIBS session. Regions of interest were the bilateral DLPFC, medial prefrontal cortex, and posterior cingulate cortex. Overall, 66 NIBS sessions were performed. Findings revealed a negative significant association between cortical thickness of the bilateral dorsolateral prefrontal cortex and reaction time for both tDCS (left: P=0.045, right: P=0.037) and iTBS (left: P=0.007, right: P=0.007) compared to placebo. A significant positive association was found for iTBS and posterior cingulate cortex (P=0.03). No association was found for accuracy. Our findings provide the first evidence that individual cortical thickness of healthy subjects might be associated with working memory performance following different NIBS interventions. Therefore, cortical thickness could explain--to some extent--the heterogeneous effects of NIBS probing the DLPFC. Key words: Non-invasive brain stimulation; Cortical thickness; Individualization; Working memory; Voxel-based morphometry
Chemotherapy with G-CSF is used to mobilize peripheral stem cells in multiple myeloma (MM) patients, with plerixafor as a rescue strategy for poorly mobilizing patients. Preclinical studies suggested ...that the nonsteroidal anti-inflammatory drug meloxicam enhances the mobilization of CD34
cells. In this single-center study, we evaluated whether adding meloxicam to chemotherapy/G-CSF mobilization increases peripheral hematopoietic CD34
cell levels and reduces the need of using plerixafor. We prospectively compared two consecutive cohorts of MM patients in first remission mobilized with G-CSF and non-myelosuppressive chemotherapy with vinorelbine or gemcitabine. The second cohort additionally received oral meloxicam. The cohorts comprised 84 patients without meloxicam (-M) and 66 patients with meloxicam (+M). Meloxicam was well tolerated and associated with similar hematologic engraftment after transplantation and equal survival rates. However, the meloxicam group had higher CD34
cell levels on day 8 of the mobilization procedure (53 200 versus 35 600 CD34
cells/mL; P=0.007), and fewer patients needed >1 collection day (+M: 6 (9%) patients versus -M: 16 (19%) patients; P=0.04). This resulted in reduced plerixafor administrations (+M: 7 (11%) patients versus -M: 18 (21%) patients; P=0.03) and less costs. Our data suggest that meloxicam enhances the mobilization of hematopoietic CD34
blood cells in MM patients.
Mountain glaciers sample a combination of climate fields - temperature, precipitation and radiation - by accumulation and melting of ice. Flow dynamics acts as a transfer function that maps volume ...changes to a length response of the glacier terminus. Long histories of terminus positions have been assembled for several glaciers in the Alps. Here I analyze terminus position histories from an ensemble of seven glaciers in the Alps with a macroscopic model of glacier dynamics to derive a history of glacier equilibrium line altitude (ELA) for the time span 400-2010 C.E. The resulting climatic reconstruction depends only on records of glacier variations. The reconstructed ELA history is similar to recent reconstructions of Alpine summer temperature and Atlantic Multidecadal Oscillation (AMO) index, but bears little resemblance to reconstructed precipitation variations. Most reconstructed low-ELA periods coincide with large explosive volcano eruptions, hinting at a direct effect of volcanic radiative cooling on mass balance. The glacier advances during the LIA, and the retreat after 1860, can thus be mainly attributed to temperature and volcanic radiative cooling.
The rapid drainage of supraglacial lakes introduces large pulses of meltwater to the subglacial environment and creates moulins, surface-to-bed conduits for future melt. Introduction of water to the ...subglacial system has been shown to affect ice flow, and modeling suggests that variability in water supply and delivery to the subsurface play an important role in the development of the subglacial hydrologic system and its ability to enhance or mitigate ice flow. We developed a fully automated method for tracking meltwater and rapid drainages in large (> 0.125 km super(2)) perennial lakes and applied it to a 10 yr time series of ETM+ and MODIS imagery of an outlet glacier flow band in West Greenland. Results indicate interannual variability in maximum coverage and spatial evolution of total lake area. We identify 238 rapid drainage events, occurring most often at low (< 900 m) and middle (900-1200 m) elevations during periods of net filling or peak lake coverage. We observe a general progression of both lake filling and draining from lower to higher elevations but note that the timing of filling onset, peak coverage, and dissipation are also variable. Lake coverage is sensitive to air temperature, and warm years exhibit greater variability in both coverage evolution and rapid drainage. Mid-elevation drainages in 2011 coincide with large surface velocity increases at nearby GPS sites, though the relationships between ice-shed-scale dynamics and meltwater input are still unclear.
Current understanding of ice dynamics predicts that increasing availability and variability of meltwater will have an impact on basal motion and therefore on the evolution and future behavior of the ...Greenland ice sheet. We present measurements of ice deformation, subglacial water pressure, and surface velocity that show periodic and episodic variations on several time scales (seasonal, multiday, and diurnal). These variations, observed with GPS and sensors at different depths throughout the ice column, are not synchronous but show delayed responses of ice deformation with increasing depth and basal water pressure in antiphase with surface velocity. With the help of a Full‐Stokes ice flow model, these observations are explained as ice motion in a caterpillar‐like fashion. Caused by patches of different basal slipperiness, horizontal stress transfer through the stiff central part of the ice body leads to spatially varying surface velocities and ice deformation patterns. Variation of this basal slipperiness induces characteristic patterns of ice deformation variability that explain the observed behavior. Ice flow in the ablation zone of the Greenland ice sheet is therefore controlled by activation of basal patches by varying slipperiness in the course of a melt season, leading to caterpillar‐like ice motion superposed on the classical shear deformation.
Key PointsDiurnal and longer‐term variations in ice deformation during summerVariations are a reaction to nonlocal changes in basal slipperinessOut‐of‐phase behavior of subglacial water pressure and surface velocity
Summary
Background
One to three percent of patients exposed to intravenously injected iodinated contrast media (CM) develop delayed hypersensitivity reactions. Positive patch test reactions, ...immunohistological findings, and CM‐specific proliferation of T cells in vitro suggest a pathogenetic role for T cells. We have previously demonstrated that CM‐specific T cell clones (TCCs) show a broad range of cross‐reactivity to different CM. However, the mechanism of specific CM recognition by T cell receptors (TCRs) has not been analysed so far.
Objective
To determine how T cells specifically recognize CM.
Methods
CM‐specific TCCs were generated from human blood of three CM‐allergic patients and a specific TCR was transfected into a mouse T cell hybridoma. Functional analysis such as proliferation assays, IL‐2 secretion assays, and calcium influx experiments were performed using irradiated, glutaraldehyde‐fixed, CM‐pre‐incubated, human leucocyte antigen (HLA)‐DR‐matched or ‐mismatched antigen‐presenting cells (APCs), and HLA‐blocking antibodies.
Results
We identified two mechanisms of T cell stimulation: some TCCs and the transfectant reacted to CM independent of uptake by APCs because proliferation/IL‐2 secretion occurred in the presence of glutaraldehyde‐fixed APCs, and intracellular calcium increased within seconds after drug addition. Other TCCs required functional APCs, compatible with uptake and presentation of CM on MHC‐class II molecules, as implied by three findings: (1) glutaraldehyde fixation of APCs abrogated presentation; (2) CM could not be washed away from CM‐pre‐incubated APCs; and (3) the optimal pulsing time was 10–20 h. Because allogeneic, MHC‐matched, CM‐pulsed APCs could induce proliferative responses as well, the ability of CM uptake and presentation is not unique to APCs from patients with CM‐induced delayed hypersensitivity.
Conclusion
Our data suggest that CM may be stimulatory for T cells either by direct binding to the MHC–TCR complex or by binding after uptake and processing by APCs. This questions the assumed inert nature of CM.
Cite this as: M. Keller, M. Lerch, M. Britschgi, V. Tâche, B. O. Gerber, M. Lüthiuthi, P. Lochmatter, G. Kanny, A. J. Bircher, C. Christiansen and W. J. Pichler, Clinical & Experimental Allergy, 2010 (40) 257–268.
A range of englacial temperature measurements was acquired in the Monte Rosa area at the border of Switzerland and Italy in the years 1982, 1991, 1994, 1995, 1999, 2000, 2003, 2007 and 2008. ...Englacial temperatures revealed no evidence of warming at the firn saddle of Colle Gnifetti at 4452 m a.s.l. between 1982 and 1991, the 1991 to 2000 period showed an increase of 0.05 °C per year at a depth of 20 m. From 2000 to 2008 a further increase of 1.3 °C or 0.16 °C per year was observed, indicating that the amount of infiltrating and refreezing meltwater at Colle Gnifetti has probably increased since 2000. The measured temperatures give clear evidence of firn warming since 1991. This is confirmed by five existing boreholes with measured temperature down to bedrock, which were drilled in 1982, 1995, 2003 and 2005. All the observed temperature profiles show a slight bending to warmer temperatures in their uppermost part indicating a warming of the firn, which can be related to the observed atmospheric warming in the 20th century. However, the drilling sites on Colle Gnifetti are still located in the recrystallisation-infiltration zone. A much stronger warming of 6.8 °C or 0.4 °C per year was found at locations beneath Colle Gnifetti on Grenzgletscher from 1991 to 2008. This warming is one order of magnitude greater than the atmospheric warming and can be explained only by a strong increase in the latent heat input by infiltrating and refreezing meltwater. The observations indicate that since 1991, an important firn area beneath Colle Gnifetti has already undergone a firn facies change from the recrystallisation-infiltration to the cold infiltration zone due to an increasing supply of surface melt energy.
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